How to modify an xml document and return it as a string in java?

Question

I have this string containing my request xml. I want to delete below "id" tags from this string if they exist and return it back. Removing "Identity" completely will also work, if that can be done.

To be deleted :
 <Identity>
<id extension="7865232" aan = "BUH"/>
<code/>
</Identity>
<Identity>
<id extension="88769032" aan = "DIH"/>
<code/>
</Identity>

String XMLString= "<request version ="1.0">
<minMatch>
<val>100</val>
</minMatch>
<paramList>
<payLoad display = "Full" type="F">
</payLoad>
<IQC code = "2">
</IQC>
<Control display="Default" type = "D">
</Control>
<member>
<memCode code = "Active"
</memCode>
<id extension="12345" aan="ACC"></id>
<id extension="54321" aan="REQ"></id>
<id extension="554376" aan="PDR"></id>
<id extension="66321" aan="NJQ"></id>
<addr use = "H">
<streetLine>123</streetLine>
<city>POLIS</city>
<state>NY</state>
<postalCode>44321</postalCode>
</addr>
<telecom value = "5543213">
</telecom>
<Person>
<name>
<given>JOHN</given>
<family>BILL</family>
</name>
<GenderCode code ="M" display="Male">
</GenderCode>
<birthime vaue="19651002">
</birthime>
<Identity>
<id extensio="7865232" aan = "BUH"/>
<code/>
</Identity>
<Identity>
<id extensio="88769032" aan = "DIH"/>
<code/>
</Identity>
</Person>
</member>
----
---
</request>"

I am using below code to achieve the same but it's not working and giving me The constructor DOMSource(Document) is undefined. I tired converting document into a byte Array but that's also not working.Is there any way i can simply do this in Java 1.8. Any other approach is also welcome. Please suggest.Thank you!

public void removeIds(String xmlString){

Document doc = null;
SAXBuilder saxbuilder = new SAXBuilder();

try{
doc = saxbuilder.build(new StringReader(xmlString));
}catch(JDOMException je){
je.printStackTrace();
}catch(IOException ie){
ie.printStackTrace();
}

Element rootNode = doc.getRootElement();
IteratorIterable<Element> rootChildren=rootNode.getDescendants(new ElementFilter("Person"));

for(Element Person:rootChildren){
 for(Element Identity:Person.getChildren("Identity")){

((Element) doc.getRootElement.getDescendants(new ElementFilter("Identity"))).removeChild("id");

  }
}

try{

TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer;
        
            transformer = tf.newTransformer();

            // transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

            StringWriter writer = new StringWriter();
            transformer.transform(new DOMSource(doc), new StreamResult(writer));
            String output = writer.getBuffer().toString();
            return output;
        } catch (TransformerException e) {
            e.printStackTrace();
        }
        
       
    }

Answer 1

Since you're invoking a transformation anyway, it's much simpler to do all the work in XSLT rather than fiddle about with low-level DOM manipulation.

If you use XSLT 3.0 (Saxon) then the stylesheet is simply

<xsl:transform version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:mode on-no-match="shallow-copy"/>
  <xsl:output indent="yes" encoding="utf-8"/>
  <xsl:template match="id"/>
</xsl:transform>

You can supply the input to this transformation as new StreamSource(new StringReader(xmlString)) -- there's no need to construct a DOM first.

It can be done in XSLT 1.0 too (ie with Xalan, which comes bundled with the JDK), but is a bit more verbose.

Answer 2

Here is solution using XPath API. In this example all elements "id" inside elements "Identity" are removed (XPath expression "//Identity/id"). If you want to remove all id elements, change it to "//id".

import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;
import org.xml.sax.InputSource;

// function for XML serialization
public static String serialize(Document document) {
        removeWhitespaces(document.getDocumentElement());
        try (StringWriter writer = new StringWriter()) {
            StreamResult result = new StreamResult(writer);
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            transformer.setOutputProperty(OutputKeys.METHOD, "xml");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
            transformer.transform(new DOMSource(document), result);
            return writer.toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    
    // helper function for stripping whitespaces
    public static void removeWhitespaces(Element element) {
        NodeList children = element.getChildNodes();
        for (int i = children.getLength() - 1; i >= 0; i--) {
            Node child = children.item(i);
            if (child instanceof Text
                && ((Text) child).getData().trim().isEmpty()) {
                element.removeChild(child);
            } else if (child instanceof Element) {
                removeWhitespaces((Element) child);
            }
        }
    }

Main code:

    // parse XML
    DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    Document doc = db.parse(new InputSource(new StringReader(xml)));
    
   // find id elements
    XPathExpression xpath = XPathFactory.newInstance().newXPath().compile("//Identity/id");
    NodeList nodes = (NodeList)xpath.evaluate(doc, XPathConstants.NODESET);

    // remove found elements
    for(int i = 0; i < nodes.getLength(); i ++) {
        Node node = nodes.item(i);
        node.getParentNode().removeChild(node);
    }
    
    // serialize and output document
    String result = serialize(doc);
    System.out.println(result);